Lighting device



Dec. l5, 1942. E. K. NAS-IER 2305943? LIGHTING DEVICE Filed June 9, 1941 Patented Dec. 15, 1942 2,305,487 ucnjrmo novios Bert K. Naster, Chioago,lll.

Application June 9, 1941, Serial N0. 397,204

8 Claims. (01.176-124) This invention relates to a lighting device, and more particularly to a device in which at least two fluorescent lamps are employed, and in which the current inzeach lamp is in diierent phase.

Since the light output of a fluorescent lamp is diminished as the magnitude of the alternating current energizing it diminishes and is zero when the current is zero, asingle lamp will have a pulsating light emission which corresponds to twice the frequency of the source of electrical energy, there being 120 pulsations oft light on a 60 cycle per second power supply. This creates a noticeable stroboscopic effect. However, it has been common in the past to use a pair of lamps in one unit, one of the lamps being in` a circuit in which the current is in leading phase rela tionship to the current in the circuit of the other lamp. In this way one of the lamps is caused to have strong light emission at the instant the current is changing direction in the other. in this way the stroboscopic eect is minimizeda However, in the arrangements previously proe posed, several difficulties have been encountered. ln order to cause the current in one `circuit to be leading a condenser has been employed in this circuit, and in operation a high voltage is built up across this condenser requiring that it be constructed for such high voltages. A more serious objection is that the wave form of the voltage developed across the lamp in the leading circuit has been irregular, having a depression near the middle or the half cycle, and so causing a loss of power resulting in substantially decreased brilliancy in this lamp. The disadvantage oi' having one lamp of lesser brilliancy in a device of this character is self-evident.

An object of the present invention is to provide a device in which the lamps will be of substantially equal brilliancy and will deliver a maximum of light output for the energy supplied and with relatively equal current in .each lamp. A further object is to provide a device of this nature which is economical of construction and conservative of space and materials. Another object is to provide a device in which the leading circuit will not require a condenser adapted for such high voltage.v Still other objects will appear as the specification proceeds.

An embodiment of the invention is illustrated by the accompanying drawing in which:

Figure 1 is a wiring .diagram of the device; Figure 2, a plan view of the transformer here employed, showing the specific arrangement of the coils; Figure 3, a diagram showing the form oi the voltage across the lamp in the leading circuit when another type of transformer is employed; and Figure 4, a diagram showing the wave form of the voltage across the lamp in the leading circuit when the transformer illustrated in Figure 2 is employed.

As illustrated, the device includes an autotransiormer A of elongated high reactive design. Figure 2 shows the physical aspects of the transformer and Figure l shows schematically the electrical connections and arrangement. The core itl may be laminated and is of'generally rectangular cross section, and has coils about each of its sides or legs ii and l2.

The two primary coils P1 and P2 extend about different legs of transformer A and are connected in series with the terminals and Y which conn stitute a source or alternating current. The windings of coils Pi and P2 are in such direction as to aid each other in building a magnetic :delai within the transformer core.

' it will be observed that the coils imi and P2 are in staggered relation, and directly opposite these coils are the secondary coils C; and Cz. IMous the coils P1 and C1 are opposite each other on different legs and at the extreme end of the core. Just adjacent these coils are the coils Pz and C2 also opposite each other. The end i3 oi coil @s is connected to the terminal Y of the alternating 'current source. The other end of this coil is connected with one end of the winding of coil C1. The direction of the windings in coils Ci and C'z are such as to build a magnetic field opposing the field provided by the primary windings. `The end l of coil C1 is connected in series with the capacitor I5, which in turn is connected through laments It and il of the iiuorescent lamp I8, to the terminal X of the alternating?, current source. A resistor 2l is connected across the capacitor I5 to discharge any residual charges left on the condenser. A switch '28 of the usual type is placed in connection between filaments of the lamp which is designed to open after the lamp has started to operate.

Toward the other end of the transformer A are the secondary coils L1 and La. These coils are adjacent the coils P: and C2 and are disposed opposite each otherl on dilerent legs of the transformer core. Like the first-mentioned secondary coils, these coils are connected in series, the end 20 of coil L1 being connected to terminal Y of the source of alternating current, their windings being in such direction that each builds a magnetic eld opposed to the field of the primary windings. The end 2i of coll La is connected through rilaments 22 and 23 of the lamp 24 to the terminal X of the alternating omtrent source. The usual switch liti is provided to open the connection icetween the lamp filaments after it has lighted.

The preferred physical arrangement oi the coils on the transformer core le shown in Fie. 2. The paper straps 26 are here used to securely blncl the coils to form a strong structure and to further insulate the coils from the grounded case. In the embodiment illustrated, the primary coils Pi and P2 are composed oi 1090 turns each, the secondary coils C1 and Cz of 1145 turns each, and the secondary coils Li and Lz of 915 turns each. The source of alternating current may be of the ordinary 11G-115 volt A. C. source, and the lamps each may be, for example, a standard 40 watt 'fluorescent lamp. It is expected, of course, that these factors, such as the number of turns on the different windings, the voltages employed and the size of the lamps, condensers, etc., may be varied to suit the particular situation While still 'obtaining the advantages of this invention.

The lamp 24 is served by a circuit including terminal X. coils L1 and L2 and terminal Y; and the lamp I8 is served by a circuit including terminal X, coils C1 and C2, capacitor l5, and terminal Y. Thus, both lamp circuits are provided with inductors which serve 4to check the current. However, only the circuit serving the lamp it has a capacitor, and the effect of this capacitor is to change the phase in this circuit, making the current in this circuit lead the current in the circuit of the otherlamp. ln this Way each o the lamps is caused to be at substantially full intensity at the instant the current at the other is changing direction and is at a minimum.

ln operation ci the device, l find that each of the lamps lil and. 2li burn. with substantially the same hrilliancy, and. that the voltage across the capacitor is much lower than would "ce expected. irorn experience with prior devices oi this The improved operation is attributed to the novel arrangement of the coils. With the interrelationship of the coils here provided, the circuit characteristics in each circuit are made more suitn and result in the improvements here made possible. lt may be noted that the magnetic coupling between the primary coils and the secondary coils Ci and Cs is substantially closer than the coupling between the primary coils and the secondary coils Li and La.

in improved efiect is also obtained by other coil arrangements than those herein specifically described and Where the coupling oi? a winding or windings corresponding with coils Li and La are less closely coupled with a primary winding than is a winding or windings corresponding with coils C1 and Cz, as, for example, an arrangement Where coils corresponding with Li and lo are on one side oi? the primary and coils corresponding with C1 and C2 are on the other side, the coils corresponding with Li and La being spaced a greater distance along the core from the primary coils and so more loosely coupled.

It is my belief that the improvement in the wave form is due to a shift in the prominence of the individual harmonies, such as the 3rd, 5th, and higher harmonies, which is produced by the change in the coupling between the secondary coils of the lamp circuits and the transformer primary coils, but it is not intended to disclaim any part of my invention should the advantages obtained be better explained on some other theory.

To demonstrate the improvement of the present arrangement, the voltage wave form across ascuas? 'the lamp in the circuit including the capacitor was compared by oscillograph with the wave form oi the voltage across a lamp in a corresponding circuit where the coils P1 and Cz were interohanged. In this other arrangement a pair of secondary coils were on each end of the transformer, the primary coils being in the center and equally spaced from each secondary, and the resulting wave form of the voltage across the lamp in the leading circuit is shown in Figure 3 of the drawing. Note that the Wave contains a serious depression near the center of the half cycle. This depression represents a considerable loss of power, and this results in substantially decreased brilliancy oi the lamp in this leading circuit.

, In the arrangement as herein set out in the present invention, the wave form of the voltage across the lamp in the leading circuit is shown in Figure 4. Note that the depression characteristic of the wave form in Figure 3 does not appear in Figure 4. This improved Wave form is substantially the same as the wave form of the voltage across the lamp in the other or lagging circuit. Thus with the improved voltage wave the lamps r give equally good performance and will balance each other to good effect.

Also the improved arrangement permits the use of a smaller capacitor in the leading circuit. In comparing the voltage across the capacitor at the same times as the Wave forms in Figures 3 and 4 were taken, it was found that with the condition represented by Figure 3 where the primary windings Wore in the center with the secondares on each side, the voltage across the capacitor was 330 volts; whereas with the condition represented by Figure 4, with the coil arrangement shown in Figure l, the voltage across the condenser was only 230 volts. This difierence in voltage requirement enables a very considerable saving in material and expense in the construction of the device.

While have shown and described in detail a specilc embodiment oi` my invention, it is to be understood that many changes and shifts may be made and the construction may take various forms, yet obtaining the improvements herein set forth and all within the spirit of the invention.. Though the invention has been described only in connection with fluorescent lamps, it is also applicable in the same manner when neon, argon, or like gaseous lamps are employed.

What claim is:

i. A fluorescent lighting device comprising a source of electrical energy, an elongated magnetlc circuit, a primary coil on one leg oi said circuit and connected to said source, a secondary coll on the other leg of said circuit and disposed opposite said primary coil, a fluorescent lamp and a capacitance connected in series with said secondary coil and said source, another secondary coll on said magnetic circuit and disposed endwise of said coils, and a second fluorescent lamp connected in series with said last-mentioned coil and said source, said 1ast-mentloned secondary coil being less closely coupled magnetically with said primary coil than is said rstmentioned secondary coil.

2. A fluorescent lighting device comprising a source of electrical energy, an elongated magnetic circuit, a pair of primary coils on different legs of said circuit andA connected with said source, a pair of secondary coils on different legs of said circuit and disposed opposite said primary coils, a iluorescent lamp and a capacitance connected in series with said secondary coils and said source, a'second pair of secondary coils on said magnetic circuit and disposed endwise of said primary and secondary coils, and a second fluorescent lamp connected in series with said second pair of coils and said source, said second pair of secondary coils being less closely coupled magnetically with said primary coilsthan is said first-mentioned secondary coils.

3. A fluorescent lighting device comprising a source of electrical energy, a primary'coil ccnnected with said source, a circuit containing a `fluorescent lamp a capacitance and a secondary connected to said source. and said last-mentioned secondary coil being magnetically coupled with said primary coil to a lesser extent than said first-mentioned secondary coil.

4. A fluorescent lighting device comprising a source of electrical energy, a primary coil connected with said source, a circuit containing a iluorescent lamp a capacitance and a secondary coil in series connection, said circuit being connected to said source, said secondary coil being magnetically coupled with said primary coil, and a second circuit containing a fluorescent lamp and a secondary coil, said second circuit being connected to said source, said last-mentioned secondary coil being magnetically coupled with said mst-mentioned secondary coil and with said primary coil but being coupledto said primary coll less closely than said first-mentioned secondary coil.

5. A fluorescent lighting device comprising a vsource of electrical energy, a primary coil connected to said source, a circuit containing a iluorescent lamp a capacitance and a secondary coil in series connection, said circuit being connected to said source, said secondary coil being magnetically coupled with said primary coil, and

and a secondary coil,l said second circuit being connected to said source, said last-mentioned secondary coil being magnetically coupled with said primary coil but being farther removedfrom said primary coil than is said first-mentioned secondary coil.

, 6. A iluorescent lighting device comprising a source of electrical energy. an elongated magnetic circuit, a primary coil embracing said circuit at its one end portion, said coil being connected with said source, a fluorescent lamp a capacitance and a secondary coil connected in series with said source, said secondary collengaging said magnetic circuit at said one end portion near said primary coil, a second uorescent lamp and a second secondary coil connected in series with said source, said second secondary coil engaging said magnetic circuit at its other end portion removed from said primary coil, and being less closely coupled magnetically with said 1 primary coil than is said first-mentioned secof electrical energy, said last-mentioned seconda second circuit containing a uorescent lamp Y ary winding being less closely coupled magnetically with said primary winding than is said mst-mentioned secondary winding.

8. In a lighting device, an autotransformer having a primary and two secondary windings, an electrical circuit including a lamp, a capacitance, and one of said secondary windings, and a second electrical circuit including a lamp and 'the second of said secondary windings, said second winding being linked by fewer magnetic lines of force developed by said primary winding than is said first-mentioned secondary winding.

BERT K. NASTER. 

